As has been conventionally known, there is a method for manufacturing a bottle containing a content fluid, including: the molding step of biaxially stretching a preform in a heated state by injecting the content fluid into the preform through a mouth portion thereof so as to form a bottle; and the sealing step of fitting a cap body to the mouth portion so as to keep the content fluid sealed. (Refer to Patent Literature 1, for example.)
Furthermore, synthetic resin containers that are made of polyethylene terephthalate (PET) resin or the like and are made by blow molding have been conventionally and widely used. Such a container is filled with a content fluid, namely a liquid such as a beverage, and sealed at the mouth portion with a cap, and then, is placed for sale in the stated condition. The product filled with a liquid such as a beverage as described above, with the mouth portion being sealed, is collectively referred to below as a filled container.
From the viewpoint of resource and energy saving, there is a need for further weight reduction of the container of the kind. However, the weight reduction requires reduction in thickness of a circumferential wall of the container. When an inside of the filled container is particularly in a reduced pressure state, buckling strength is deteriorated, possibly resulting in deformation or breakage of the container under load applied during transportation.
Patent Literature 2 discloses a method for preventing deformation and breakage of containers. Specifically, a drip of liquid nitrogen is added into a bottle container when the container is filled with a content fluid and is sealed with a cap. Then, due to vapour pressure of the added liquid nitrogen, the inside of the container is placed under a pressurized state, that is, a so-called positive pressure state.
Patent Literature 3 also discloses a method for blow molding a preform with use of a liquid, instead of air, as a pressure medium.
In the molding method, since a content fluid that is to be filled in a final product may be used as the pressure medium, a filling step may be omitted, and a production line may be simplified.
FIG. 10 is a schematic view illustrating a blow molding device configured to blow mold a preform with use of a liquid as the pressuring fluid.
A part A of the device includes a metal mold 1101, a blow nozzle 1104, and a stretching rod 1108 that is inserted in the blow nozzle 1104 and that is used for vertically stretching the preform. As auxiliary equipment for supplying a pressurized fluid, a pressurized liquid supply unit 1122 and a liquid supply unit 1123 are provided adjacent to the part A.
The pressurized liquid supply unit 1122 is in the form of a plunger pump and operates by utilizing, as a power source, a pressurized fluid Fp supplied from a pressurizing device 1121 such as a pressurizing pump, a compressor, or the like, through a pipe P101. The pressurized liquid supply unit 1122 supplies the pressurized liquid L to an inside of a preform 1031 that is externally fitted to a tip portion of the blow nozzle 1104 tightly, through a pipe P102, an electromagnetic valve V102, and the blow nozzle 1104.
The liquid supply unit 1123 supplies, to the pressurized liquid supply unit 1122 through a pipe R101, the liquid L that is regulated to be a predetermined temperature.
As a result of the vertical stretching by means of the stretching rod 1108, and inflation and stretching by means of the pressurized liquid L, the preform 1031 is shaped in accordance with a shape of a cavity 1102 of a metal mold 1101, and thus, a container 1041 is molded.
With their numerous excellent characteristics, blow molded bottles made of polyethylene terephthalate (PET) resin (so-called pet bottles) have been conventionally used as bottle containers in a variety of fields.
Containers of such a kind are molded by expandingly stretching and deforming a preform that has been inject molded into a bottomed tubular shape, in a state where the preform is heated to a temperature at which a stretching effect is achieved.
In detail, as illustrated in FIG. 20 (which corresponds to FIG. 12 in Patent Literature 4), a preform 2031 that is heated to a temperature at which the stretching effect is achieved is fitted to a blow metal mold 2101, with a mouth portion 2032 being projected upward and with a neck ring 2033 being engaged with a neck support flange portion 2103, the neck ring 2033 being integrally formed around a lower end on an outer circumferential surface of the mouth portion 2032 of the preform 2031. A guide tubular portion 2110, which is a tip portion of a blow nozzle 2105, is loosely engaged into the mouth portion 2032 of the preform 2031. In the above state, the preform 2031 is stretched in an axial direction by means of a stretching rod 2116 that is inserted through an insertion hole 2111 provided through a middle of the blow nozzle 2105, and the preform 2031 is also stretched in a radial direction by means of blow air that is a pressurized fluid supplied to the preform 2031 through the insertion hole 2111. Thus, the preform 2031 is molded into a bottle container 2041.
Patent Literature 3 also discloses an invention of a method for blow molding a preform by using a liquid, instead of blow air, as the pressurized fluid.
In the above molding method, by using a content fluid that is to be filled in a final product as the liquid, a filling step may be omitted, and a production line may be simplified.